1. Field of the Invention
The present invention relates to a working fluid processing device in a wire electric discharge machine, and particularly to technology for safely and easily performing the maintenance and management of filters in such a working fluid processing device.
2. Description of the Related Art
Upon performing electric discharge machining with a wire electric discharge machine, a working fluid (usually water) is used for maintaining the insulation between an electrode and a work piece, and eliminating chips generated pursuant to machining. The working fluid (impure water) containing chips or sludge such as dust that crept in is guided to a filter via a holding tank, and sludge is thereby filtered and eliminated. The working fluid cleaned with the filter is re-supplied to the processing unit via a fresh-water tank for storing the clean working fluid.
A filter becomes gradually clogged pursuant to the prolonged use thereof, and the pressure applied to the filter increases in accordance with the clogging. A dangerous state is generated when the increase in pressure exceeds the limit, and, as a result, it is not unusual for accidents to occur which are caused by the breakage or falling-off of filters and hoses.
In order to prevent such incidents, conventionally, as shown in FIG. 1, a water pressure gauge for measuring filtration pressure was disposed in the flow path between a filter pump, which aspirates impure water from a holding tank storing such impure water generated at the processing unit and supplies the filter with this impure water, and the filter, and an operator visually confirmed the pressure indication of such water pressure gauge.
In other words, the operator visually read the filtration pressure at the time of commencing the processing or the like, and changed the filter if the filtration pressure has reached a replacement pressure (a reference pressure value set for determining the necessary point of time for replacing the filter). Moreover, as a substitute of this type of water pressure gauge checking, there is a method of employing an accumulated operating time of a filter as an object to be checked, and replacing the filter if the operating time has reached the replacement time (reference time established for determining a necessary point of time for replacing the filter).
However, in general, a filtration pressure appearing between a filter and a filter pump during a continuous machining or immediately after the completion of machining differs from the filtration pressure at a time a suspension time has elapsed after the stoppage of the continuous machining, even if the degree of progress in filter clogging is the same. This is because the sludge attached to the filter element inside the filter is detached upon the depressurization caused by the suspension of the pump, or the attachment of such sludge is temporarily loose.
Naturally, a high filtration pressure will not be displayed easily even if the operator visually checks a water pressure gauge in such a situation. Thus, when the operator restarts machining without anxiety, the filter element is pressurized, and gradually returns to the original filter pressure. And, when the machining is further continued, there is a possibility that the pressure applied to the filter may increase to a dangerous level. During such time, if the operator fails to confirm the pressure due to reasons of nighttime operation or the like, rupture accidents and so on may actually occur.
As described above, even if an operator visually confirms the pressure value shown on a water pressure gauge, such value will vary largely depending on the timing of such visual confirmation, so that there is a possibility that the value will not accurately reflect the progress of filter clogging. Therefore, filter replacement time cannot be reliably determined.
Further, since the progress of filter clogging will vary depending on conditions such as the amount of chips generated per unit machining time, it is not possible to adequately determine filter replacement time relying upon the checking of an operating time (accumulated machining time).
An object of the present invention is to improve a working fluid processing device of a wire electric discharge machine which can provide an operator with information necessary for determining filter replacement time.
The present invention achieves the foregoing object by disposing a pressure detection sensor between a filter pump and a filter in a working fluid processing device of a wire electric discharge machine, and, by processing the water pressure information with a controller, providing an operator with useful information for determining filter replacement time.
In other words, the present invention is applied to a working fluid processing device of a wire electric discharge machine which supplies an electric discharge processing unit with working fluid stored in a fresh-water tank via a supply channel on the one hand, and temporarily stores the working fluid used in the electric discharge processing unit in a holding tank on the other hand, and enables the working fluid to return to the fresh-water tank via a pump and a filter, and improves this device as described in the following embodiments.
With the first embodiment of the present invention, a sensor for detecting a filtration pressure of the filter is provided, and the water pressure transition is recorded based on the output of the sensor. As a result, an operator can know the filtration pressure of a filter from the present time (time of confirming the recorded contents) by tracing an elapsed time. Therefore, unlike conventional technology where only an instantaneous value at the time of visually checking a water pressure gauge can be confirmed, the progress of filter clogging can be acknowledged with ease.
With the second embodiment of the present invention, a sensor for detecting the filtration pressure of the filter and display means for displaying the filtration pressure of the filter are provided, and the water pressure transition is displayed on the display means based on the output of the sensor. For example, a point of X-Y relationship, with the X-axis being the time and the Y-axis being the filter pressure, is plotted on a monitor screen in a graph format. The operator is thereby able to know the filtration pressure of the filter, at a glance, from the present time (time of confirming the recorded contents) by tracing an elapsed time.
In the foregoing second embodiment, storage means for storing, at prescribed time intervals, filtration pressure detected by a sensor may be provided so as to display the stored filtration pressure. Moreover, displaying of the filtration pressure detected by the sensor on the display means may be renewed only at the time of processing.
Further, information function of anomalies may be added to each of the foregoing embodiments. For instance, information on an anomaly may be made when the sensor detects a filtration pressure exceeding a predetermined reference. In addition, information on an anomaly may be made when the sensor detects, during operation after the commencement of operation, a filtration pressure falling below the filtration pressure detected at the time of the previous filtration pressure detection.